The present invention is directed to bicycle brake devices and, more particularly, to a hydraulic caliper brake for a bicycle.
Bicycles employ many types of brake mechanisms. For example, a typical caliper brake assembly is disclosed in U.S. Pat. No. 4,754,853. A caliper brake typically comprises a pair of brake arms, wherein each brake arm includes a brake arm mounting portion, a brake pad mounting portion and an operating portion. The brake arm mounting portion is disposed between the brake pad coupling portion and the operating portion, and the brake arm mounting portion is pivotably connected to a bicycle frame member such as the front steering fork so that the pair of brake arms are located in close proximity to the front wheel. A brake pad is mounted to the brake pad mounting portion for applying frictional force to the wheel rim, and an operating wire assembly is connected to the operating portion. The operating wire assembly is connected to a control lever assembly mounted to the bicycle handlebar so that the rider may pull and release a control lever to operate the brake mechanism.
Some bicycles substitute a hydraulic operating system for the operating wire assembly. For example, German Offenlegungsschrift No. 3,325,970 discloses a caliper brake wherein a hydraulic cylinder assembly is disposed between the operating portions of a pair of brake arms that support a corresponding pair of brake shoes. The hydraulic cylinder assembly comprises first and second pistons slidably disposed within corresponding first and second opposing bores formed in a housing, wherein the outer end of each piston engages the operating portion of a corresponding brake arm. The first and second bores are in fluid communication with a hydraulic fluid chamber so that the first and second pistons move outwardly in opposite directions when hydraulic fluid is injected into the hydraulic fluid chamber, thereby rotating the brake arms and the brake shoes into their operating positions.
Caliper brakes usually are designed so that the brake shoes will be located close to the wheel rim when the brake is mounted to the bicycle. Such designs allow the rider to apply the brakes rapidly with little movement of the manually-operated control lever. However, since the tire is wider than the wheel rim, such placement of the brake shoes makes it difficult, if not impossible, for the wheel to be removed for servicing. To overcome this problem, some caliper brakes are designed so that the hydraulic cylinder assembly can be moved or removed, thereby allowing the brake arms to be spread outwardly and allowing the tire to pass through the gap between the brake shoes. However, known designs usually require the rider to unscrew one or more nuts or bolts and manipulate the hydraulic cylinder assembly accordingly, thereby making wheel removal more complicated than it should be.